BANGKOK -- The Red Shirt protest movement and the embattled Thai government sought ways to head off an all-out conflict Monday as street battles dragged on for a fifth day and thousands of protesters ignored a government ultimatum to leave their huge, fortified encampment in central Bangkok.

An aide to Thai Prime Minister Abhisit Vejjajiva said a Red Shirt leader called him and proposed a cease-fire to end fighting that has killed 37 people and injured at least 266 since Thursday, when the latest violence in a two-month stand-off erupted, the Associated Press reported. The aide, Korbsak Sabhavasu, said he received a call from Red Shirt leader Nattawut Saikua and told him that if the protesters retreated to their encampment, soldiers would not fire at them, AP said.

Earlier, Nattawut said the Red Shirts were ready to negotiate, and another protest leader called for intervention by Thailand's ailing king, Bhumibol Adulyadej. The Red Shirts have been occupying a swath of central Bangkok since March to press demands for Abhisit's resignation and new elections. At least 66 people have been killed and more than 1,600 injured since the protests began.

It was not immediately clear whether the tentative contacts would resolve the impasse, which appeared to be headed toward an escalation earlier Monday when both sides ruled out face-to-face talks.

A small government plane dropped leaflets demanding that the protesters abandon their encampment or face criminal charges, but the estimated 5,000 people there refused to budge, and sporadic fighting was reported. Before dawn, explosions and bursts of gunfire were heard outside the luxury Dusit Thani Hotel bordering the protest zone, and guests were rushed to the basement for safety.

The tensions escalated further Monday morning with the news that Maj. Gen. Khattiya Sawasdipol, a renegade army officer and high-profile member of the protest movement, had died in a hospital four days after being shot in the head by a sniper.

The latest casualties included the first soldier to die in the current spate of violence. He was reported killed Monday morning in unclear circumstances.

The shooting of Khattiya, who was regarded as extreme even by his political allies, enraged the protesters' militant wing. He was the first victim of the latest round of violence, which started Thursday night when the government attempted to cordon off the sprawling protest site and prevent supplies and reinforcements from reaching it.

On Sunday, the leaders of the United Front for Democracy Against Dictatorship, as the red-shirted protesters are more formally known, offered negotiations, but only if they were mediated by the United Nations and preceded by a troop pullback.

Analysts said the suggestion was never likely to be taken seriously by the government, and it was rapidly dismissed.

"If they really want to talk, they should not set conditions like asking us to withdraw troops," said Korbsak, the prime minister's aide.

Panitan Wattanayagorn, the government spokesman, rejected the idea as foreign interference in Thailand's internal affairs.